1. Field of the Invention
This invention relates to an image recording member for recording image by application of electric current thereto, which are usable in various recording methods such as those receiving signals of facsimiles, outputs of computer and its terminal equipments, and various kinds of data of measuring apparatuses for industrial, medicinal, business and other purposes.
2. Description of Prior Arts
Recording of electrical signals as an image has been increasing year by year with development in the facsimile and other telecommunication facilities. The methods which have so far been adopted most widely for such recording purposes may be represented by electrical discharge recording, electrolytic recording, and so forth.
The electrical discharge recording method is to form an image either by placing a white pigment layer on an electrically conductive black layer, or by placing an electrically conductive thin metal layer such as, for example, aluminum on the abovementioned electrically conductive black layer, and then by perforating the surface layer of the white pigment or the thin metal layer by electrical discharge of a recording needle (hereinafter referred to as "stylus") so as to remove the surface layer and to expose the black layer underneath thereof.
On the other hand, the electrolytic recording method is to form an image by first impregnating a sheet of paper with an electrolytic solution to bring the same into a wet state, and then causing electric current to flow therethrough by way of the stylus. The resulting image is either a colored substance formed by reaction between the ionized stylus metal and the electrolyte, or a colored decomposition product formed by electrolysis of the electrolyte impregnated in the paper by electric current caused to flow therethrough from the stylus.
According to the electric discharge recording method, as the surface layer is perforated by heat of electric discharge generated by the stylus, there inevitably take place various inconveniences such that a very strong irritating odor comes out, dust from perforation of the surface layer scatters, wear and tear of the stylus is considerable, and other disadvantages. Moreover, mechanical forces such as folding, pressure adhesion, etc. to be imparted to the laminated layers are liable to expose the black layer with the consequence that the paper becomes easily stained. In other aspect, since the surface layer is made so thin to facilitate the electric discharge, the black layer beneath the surface layer cannot be masked perfectly; which is liable to caused the base color of the recording paper to become greyish rather than white, thereby reducing the outer appearance or quality of the paper as a product.
On the other hand, since the electrolytic recording method is of wet type, the recording paper is inferior in its preservability. Also, the quality of the image formed thereon is deteriorated by running of the electrolyte. In addition, the paper undergoes deformation such as wrinkles formed on its surface due to drying after the image recording. These disadvantages are fatal to such wet type recording method.
Also, in Japanese Patent Publication Nos. 22341/1963 and 29630/1969, there is proposed a dry type electrosensitive recording sheet, wherein an image is obtained by dispersing metal compounds capable of being electrically reduced into a free metal in an insulative resin, followed by reduction of the metal compounds into free metals through conduction of electric current. In this electrosensitive recording sheet, however, most of the metal compounds of relatively high electric conductivity are colored, and less-colored metal compounds are of low electric conductivity. The latter require special chemical and physical treatments for the electric current to be conducted therethrough. However, such treatments bring about coloration of the metal compounds with the consequent increase in density of the base color of the recording sheet to a considerable degree. Moreover, difficulty in electric conduction through the insulative resin dispersion causes issuance of an undesirably bad smell due to heat from the electric discharge at the time of recording, considerable degree of wear and tear in the stylus, and other defects.
Furthermore, Japanese Patent Publication No. 5476/1967 and No. 13239/1967 disclose a method, wherein an electrically conductive thin layer is formed on a white or transparent substance such as silica, and so on by means of evaporative deposition, after which the substance is dispersed in a matrix for electric conduction. However, even this method requires a considerable degree of skills and facility.
As stated above, therefore, the conventional image recording methods posed various problems in forming images on the recording member in view of the lack of an image recording member capable of effectively carrying out the image formation by electric conduction in the dry type recording technique.